The present invention relates to a blank for a cup shaped container fabricated of cardboard material and of the type which comprises a bottom of substantially rectangular form, sides which extend upwardly up from the said bottom and which have rounded corners at the upper edge and an edge flange projecting obliquely downwardly from the said upper edge and extending continuously around the entire upper edge of the container. In a prior art container of this type the edge flange extending obliquely downwards from the upper edge of the container provides stabilizing of the said upper edge. Where the container is used in combination with a reclosable lid the upper edge, and the associated edge flange is subjected to mechanical wear and pressure forces thus in order to make the upper edge sufficiently strong to stand such wear and such mechanical stresses the container ought to be manufactured from a relatively strong cardboard material. In order to reduce the costs for the container it is however desired to use as thin and cheap cardboard material as possible, but it thereby may happen that the upper edge and the edge flange break especially at the long sides of the container which are most subjected to stresses of this type, whereby the long sides are bent in at the point where broken.
The manufacture of a container of this type involves special problems. In order to obtain a container having rounded corners at the upper edge the blank of the container must have a bowed or curved shape at the places corresponding to such round corners. Depending on the said bow shape the edge flange must be bent down at the same time as the container sides are folded up from the container bottom and at the same time the sides are bent to the rounded shape. If the number of material layers is increased at the edge flange and no other modifications are made of the container blank, the edge flange cannot be bent down as mentioned and instead the edge flange has to be bowed in a special operation which does not allow an even and continuous rounding of the corners of the container.